The ACA Queensland Branch were privileged to have Marilyn Lewis, a world expert on Cathodic Protection, give a talk on CP Interference. As Marilyn was in town teaching the NACE CP courses, the Queensland Branch was able to get her to share her extensive knowledge with the attendees to the event. As Marilyn herself suggested, she’s been in training for 36 years, and still finds herself learning. A large group of avid corrosionists attended the event at the Norman Hotel in Brisbane. After enjoying canapes and a few refreshments, the crowd gathered to listen to Marilyn’s talk. Marilyn began with an example of a pipe and explained that in order to understand interference between structures the engineer has to understand the following: the source of the current, know how to test it, know how to interpret the data, have confidence in the data, make a conclusion that makes sense and take appropriate action. The last action may be to “dig it up.” Marilyn then went on to describe the difference between sound engineering and what regulations say. Sometimes they are at odds. Marilyn takes an engineering point of view despite what regulations say. Marilyn then spoke about voltage gradient in the surrounding electrolyte. A problem occurs when a foreign object crosses the voltage gradient and a stray current is imposed onto a structure. The concept of remote earth and the area of influence was discussed. Rutenberg’s equation was dissected much to the delight of the attendees (a touch of hyperbole there). Many more concepts were expanded on, such as how to detect the interference and discharge of current outside the area of interference. A practical example of how to measure interference was discussed. The event was MC’s by the Queensland Branch President, Murry McCormick. Many thanks must go to the event’s sponsor, Anode Engineering.
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